1. Field of the Disclosure
The present invention relates to an organic light emitting device, and more particularly, to an organic light emitting device that emits white light.
2. Discussion of the Related Art
An organic light emitting device has a structure that an organic light emitting portion is formed between a cathode and an anode, wherein electrons are injected into the cathode, and holes are injected into the anode. If the electrons generated in the cathode and the holes generated in the anode are injected into the organic light emitting portion, an exciton is generated by combination of the injected electrons and holes, and then the generated exciton is transited from the excited state to a ground state, whereby a light photon is emitted.
Such an organic light emitting device may be used as a back light of a liquid crystal display device, an organic light emitting display device, or in general lighting. Particularly, an organic light emitting device that emits white light may be combined with color filters and used as a full color display device.
A full color display device can be created by combining a color filter with a white organic light emitting device. The organic light emitting device emitting white light may be manufactured using a deposition process for each pixel. It is advantageous in that the process may be performed without a shadow mask. When the organic light emitting device has a red pixel including a red emitting layer, a green pixel including a green emitting layer, and a blue pixel including a blue emitting layer, it is necessary to make a pattern of each emitting layer with a shadow mask. However, when the organic light emitting device has a red pixel including a white emitting layer and a red color filter, a green pixel including a white emitting layer and a green color filter, and a blue pixel including a white emitting layer and a blue color filter, it is not necessary to make a pattern of each emitting layer, thereby making it possible to perform the process without a shadow mask.
Hereinafter, an organic light emitting device emitting white light according to the related art will be described with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view illustrating an organic light emitting device according to the related art.
As shown in FIG. 1, the organic light emitting device according to the related art includes an anode 1, a first stack 2, a second stack 3, and a cathode 5.
The first stack 2 is formed on the anode 1 to emit blue (B) light. Although not shown in detail, the first stack 2 includes a light emitting layer emitting blue (B) light, a hole transporting layer for transporting holes to the light emitting layer, and an electron transporting layer for transporting electrons to the light emitting layer.
The second stack 3 is formed between the first stack 2 and the cathode 5 to emit yellow-green (YG) light. Similar to the first stack 2, the second stack 3 includes a light emitting layer for emitting yellow-green (YG) light, a hole transporting layer for transporting holes to the light emitting layer, and an electron transporting layer for transporting electrons to the light emitting layer.
The aforementioned organic light emitting device according to the related art emits white light by mixing blue light emitted from the first stack 2 with yellow-green light emitted from the second stack 3.
FIG. 2 is a cross-sectional view illustrating an organic light emitting device according to another embodiment of the related art.
As shown in FIG. 2, the organic light emitting device according to another embodiment of the related art includes an anode 1, a first stack 2, a second stack 3, a third stack 4, and a cathode 5.
The first stack 2 is formed on the anode 1 to emit blue (B) light. Although not shown in detail, the first stack 2 includes a light emitting layer for emitting blue (B) light, a hole transporting layer for transporting holes to the light emitting layer, and an electron transporting layer for transporting electrons to the light emitting layer.
The second stack 3 is formed on the first stack 2 to emit green (G) light. Similarly to the first stack 2, the second stack 3 includes a light emitting layer for emitting green (G) light, a hole transporting layer for transporting holes to the light emitting layer, and an electron transporting layer for transporting electrons to the light emitting layer.
The third stack 4 is formed between the second stack 3 and the cathode 5 to emit red (R) light. Similarly to the first stack 2, the third stack 4 includes a light emitting layer for emitting red light, a hole transporting layer for transporting holes to the light emitting layer, and an electron transporting layer for transporting electrons to the light emitting layer.
The aforementioned organic light emitting device according to this embodiment of the related art emits white light by mixing blue (B) light emitted from the first stack 2, green (G) light emitted from the second stack 3, and red (R) light emitted from the third stack 4 with one another.
However, the aforementioned organic light emitting devices according to the embodiments of the related art have a problem in that light emitting efficiency is low. Particularly, a problem occurs in that overall light emitting efficiency is lowered because of low efficiency of blue (B) light.